The present invention relates to a method and a die for bending tubular elements.
It is known in the technical sector relating to the manufacture of large-size tubular piping which is normally made by means of forging that there exists the need to obtain curved sections by means of bending of the pipe.
Although the bending methods performed for example using bending machines are per se conventional, these methods however are not suitable in the particular case where it is required to bend pipes which have relative ratios of the bending radius R and the outer diameter D of the pipe with values less than 3.
It is also known that this piping must have connecting branches extending in transverse—i.e. usually radial—directions and, particularly in the case of piping used for high-risk applications, such as nuclear power stations, these branches should not be welded to the respective pipe section after bending, but must be formed integrally therewith during forging of the pipe so as to ensure continuity of the piping and therefore avoid the risk of leakages of dangerous material.
The presence of these transverse branch extensions integral with the pipe means, however, that conventional bending machines cannot be used and in particular makes it difficult to perform bending of the pipe with the degree of precision required by the specific applications, the bending not being able to performed using normal known methods particularly in the case where the base of one or more of these branches is adjacent to the initial section of curvature of a curved section, making it particularly difficult to perform both forging of the article and subsequent bending.
The technical problem which is posed, therefore, is to provide a method and an associated die for bending pipes for piping having relative ratios R/D of the bending radius R and the outer diameter D of the pipe with values less than 3.
In connection with this problem it is also desirable that the die and method should be able to allow bending with the necessary tolerances also in the case where radial branches integral with the pipe are present during bending.
These results can be achieved according to the present invention by a method according to the characteristic features and a die according to the characteristic features provided in the description and the claims.
